This one is for the boy with the birthday celebration.

Sophia Grace Brownlee's son River is officially one—and the former Ellen DeGeneres Show star marked the milestone with a super party.

"It was better than I expected it would be and everything went to plan," the 20-year-old exclusively told E! News of the bash, which was attended by cousin Rosie McClelland. "Everyone had such a great time!"

Sophia—who rose to fame alongside Rosie back in 2011 when footage of them performing Nicki Minaj's song "Super Bass" went viral on YouTube—welcomed her first child with her longtime boyfriend in Feb. 2023.

"Mom life obviously has its hard parts but overall I wouldn't change it for the world," she shared. "I have loved watching River grow into the 1-year-old he is now and can't wait to see what the future holds for him."

"Now he's getting older, he's not just a baby that sleeps and eats anymore," the "Hollywood" singer noted, "he is starting to get his own personality which is super cute and he has his favorite people too. One of them being my dad!"

Ahead of his birthday, River had already been checking off major milestones.

"He actually started walking when he was 10 months," Sophia told E!, "which I was very proud of him for!"

"And he is a very clever little boy," she added. "Lately he has started eating proper foods now too."

In April, just over a month after becoming a mom, Sophia shared insight into her new chapter.

"Before I had the baby, people say things like, 'Oh, get your sleep while you can,' and, 'You're not going to get sleep for ages,'" she told E! at the time. "And you take it with a pinch of salt, like, 'Yeah, I know, I'm going to have to wake up in the night. But how bad can it be?' But it really is bad. Like, it's amazing, but it is very difficult."

"No one can really prepare you for how difficult it is going to be to be a mom," she continued. "But it's definitely all worth it."

Keep reading to see all of the sweet photos from River's birthday party...

—Reporting by Brody Brown.